1. Field of the Invention
The present invention relates to a light-emitting organic compound (including a complex that contains a metal in its molecular formula) capable of providing Electro Luminescence (EL), and an EL display device utilizing the same. Typically, the present invention relates to a high-molecular type EL display device which utilizes a light-emitting organic compound made of a high-molecular compound.
The present invention also relates to an electronic apparatus including the above-mentioned EL display device as its display portion. It should be noted that the above-mentioned EL display device will be also referred to as the OLED (Organic Light-emitting Diode).
2. Description of the Related Art
Development of a display device including an EL layer as a self-light emitting element that utilizes EL phenomenon (i.e., the EL display device) has been proceeded in these years. Since the EL display device is of the self-light emitting type, no back light is required to be contained therein, unlike a liquid crystal display device or the like. Moreover, the EL display device exhibits a wide viewing angle. From the above features, the EL display device is advantageous to be used as a display portion for a portable device which is likely to be used outdoors.
A light-emitting layer as a principal portion of the EL element is made of an insulating material. When a voltage is applied across a cathode and an anode with the light-emitting layer interposed therebetween, carriers (electrons and holes) are injected into the light-emitting layer and recombined to emit light. Thus, a current flowing through the light-emitting layer is caused by the recombination of carriers. An EL material that can be used for the EL display device is described in, for example, Japanese Patent Application Laid-Open No. Hei 2-311591.
In a light-emitting element such as a light-emitting diode in which a semiconductor junction is formed, Na (sodium) that may exhibit an adverse effect as a movable ion causes a resistance value of the light-emitting layer to decrease, and therefore, can cause a current flow other than that caused by the carrier recombination. When such an unnecessary current flows, an amount of heat generation is increased and the light-emitting layer is more likely to deteriorate. The same disadvantage may occur in the EL device. However, any sufficient countermeasure against the disadvantage caused by the movable ion has not been provided for the EL material.